They couldn't seem less alike, the two men sitting side by side at the counter of the trendy retro-1950's Pink Cadillac Cafe in West Hollywood. Charlie, the younger one, wears a modish dark sports jacket, a collar-buttoned
but tieless white shirt, and a targeted extrovert gaze as he reads 11 pancake options - from buckwheat to beernut to blueberry - off a wall menu. Raymond, who may be 20 years older, not quite soigne in his gray suit and dark
tie, his weary eyes seeming to look inward, says he just wants ''pancakes.'' '' 'Course,'' Charlie says. '' 'Course, the maple syrup is supposed to be on the table
before the pancakes,'' Raymond states in his flat voice.

''Ray,'' says Charlie, hefting a pitcher of maple syrup off the counter, ''Ta-da!''

''Charlie Babbitt made a joke,'' Raymond says, coaxing a heh-heh out of his throat.

''I made a joke,'' Charlie replies, smiling broadly. And small as the joke is, at that moment the ease and warmth between the two men is almost palpable.

But this scene, near the end of ''Rain Man'' - opening in New York on Friday at Loews Paramount and New York Twin - stands in sharp contrast to several earlier ones in the $24 million film in which Dustin Hoffman, 51 years old, plays
Raymond, a long-institutionalized autistic savant, and Tom Cruise, 26, is Charlie, his scheming brother.

Mr. Hoffman was associated with the project throughout its long gestation, as was Mr. Cruise. And, rather surprisingly, Raymond's unchangeability and his limited emotional palette - characteristic of autism - were not deterrents to Mr. Hoffman, whose
full-scale sea-change characters in ''Midnight Cowboy,'' ''Lenny'' and ''Tootsie,'' among other films, have won him countless accolades. In fact, it was Mr. Hoffman
who, following early research, suggested that Raymond's disability be changed from what he calls ''some unspecified form of mental retardation in the first draft I read,'' to autism.

''I accepted the fact that in order to be authentic, Raymond couldn't have the dramatic arc that actors always look for in roles,'' he says. ''And that instead of a full-scale painting, I would have to do a pen-and-ink
drawing - a poem, a haiku.''

The pancake house exchange between the brothers is, in fact, a tender variation on an acrimonious Cincinnati restaurant scene in which Charlie was apoplectic over Raymond's insistence that the maple syrup arrive before the pancakes.

That was at the beginning of the tormented weeklong cross-country automobile journey the two have just concluded. The trip is central to the opportunistic Charlie's plan to fleece Raymond, only vaguely recalled from infancy as ''Rain Man,''
out of the substantial inheritance left him by their recently deceased father.

All of Raymond's eating, sleeping, dressing and television-watching rituals that threaten to drive Charlie to distraction are, in fact, part of the older man's autism. So are his alientation and lack of self-awareness. Raymond's self-mocking
reference to maple syrup - it is actually he and not Charlie who made the joke - is a major breakthrough for him, and it is about as big an advance as one can expect in an autistic person, because, as Barry Levinson, the director
of ''Rain Man,'' says, ''Raymond is going to be Raymond; Raymond doesn't change. Somebody who's autistic doesn't suddenly become another person. He is who he is.''

The essential immutability of autistic people, plus the remoteness of those with the developmental disability, were apparent stumbling blocks to the directors Martin Brest, Steven Spielberg and Sydney Pollack. (And to their respective screenwriters.)
Each of these men was announced - and subsequently disannounced - as director of ''Rain Man'' before Mr. Levinson and Mark Johnson, the producer with whom he worked on ''Diner,'' ''Tin
Men'' and ''Good Morning, Vietnam,'' came on board early this year. (The final script credit goes to Barry Morrow, from whom the executive producers, Peter Guber and Jon Peters, commissioned the
first draft three years ago, and to Ronald Bass, who worked with Mr. Brest and who was recalled by Mr. Levinson.) Mr. Hoffman says, ''Barry was the first director who wasn't apprehensive about what I was telling
him - what I wanted to do. All the other directors, to different degrees, would say, 'Am I hearing you right: You don't want to make eye contact with anyone in the movie? And another thing: You don't talk voluntarily?'
The other directors would say, 'So how can we have scenes?' They didn't know I was getting a lot of stuff off the people I was meeting and was moved - without eye contact. 'There's a key.' I would
say. 'We can find a code. We can discover that key and put it on paper And the Charlie character can be part audience and discover the key.' ''

The eventual key, which Mr. Hoffman says came from ''real-life prototypes,'' involved how ''to force the attention and get the attention. You can't for example, be abstract: You can't say, 'What's your
favorite color?' but, rather. 'Do you like red?' ''

Nor in Raymond's case can you ask life-changing either/or questions. In a custody-hearing scene in ''Rain Man,'' he is asked by an officious psychologist (Mr. Levinson, the director, in an unbilled turn) if he would prefer to
live with Charlie in Los Angeles or go back to the institution in Ohio. He answers yes to both options.

As directors came and went and the postponement of shooting on ''Rain Man'' stretched out to 13 months beyond the date originally projected for the start of filming, Dustin Hoffman's research had become massive. Following leads
provided by Gail Mutrux, the film's associate producer, he consulted experts on autism at the Institute for Child Behavior Research in San Diego and at the U.C.L.A. Neuropsychiatric Institute as well as on the East Coast.
He spent time with autistic people (Tom Cruise and, occasionally, Martin Brest, the first would-be director of ''Rain Man,'' joined him on bowling outings with one man) and with the families of autistic
people. He studied the documentary film ''Portrait of an Autistic Young Man.'' He read books and interviewed their authors, among them Dr. Oliver Sacks, who wrote of a set of autistic twins in ''The
Man Who Mistook His Wife for a Hat.''

The research not only suggested to Mr. Hoffman that Raymond should have ''no grudges, no guile and that if he tries to be manipulative, as we all do, he does it less well.'' It also suggested which of the savant abilities - those oases
of brilliance that sometimes accompany autism - Raymond might have. The Sacks twins' ability to calculate rapidly the number of matchsticks spilled from a box became Raymond's ability to count instantly the number
of toothpicks spilled from a box in the Cincinnati restaurant scene.

Though Mr. Hoffman still claims he is ''no expert'' on autism, as preproduction rehearsals on ''Rain Man'' approached, he was feeling the duration and the weight of his investigations.

''I was very frightened because it was time to fish or cut bait,'' he says. ''The challenge then became to do what I always try to do, which is to bring it home and not try to do a character that is not myself - to find those
autistic parts of myself. Because I'm convinced that we're all a little bit autistic, just like we're all a little bit crazy.

''Think of someone sitting next to you and telling you something and obviously you're not listening. Where were you? You don't know. Or also those times where you said. 'I heard what you said' and you can even repeat it -
but you really weren't listening, you just recorded it.''

Mr. Hoffman says that bringing Raymond home ''took forever,'' but he realized the degree to which he had done so when he, ordinarily ''a very tactile person,'' felt ''little shocks when I was touched''
by co-workers between takes. ''It disturbed where I was. It was like what Temple Grandon, author of 'Autobiography of an Autistic,' told me: contrary to belief, autistics don't want not to be held and
touched. But they shrink from physical contact because it's too powerful an experience; they get little jolts.''

His own jolts aside, the actor says he knew he had internalized Raymond when he could improvise as the character. ''That is always the signal to me,'' he says.

In rehearsals, Tom Cruise could also improvise as Raymond. And Mr. Hoffman could - and did - improvise as Mr. Cruise's character. And each eventually incorporated the other's ad-libs into his own performance.

Though Mr. Cruise says that he improvised ''far more'' with Mr. Hoffman than he did with his ''other master,'' his ''Color of Money'' co-star, Paul Newman, ''and probably more than
I ever have on a movie,'' ad-libbing was not for him the ultimate challenge of ''Rain Man.''

Rather, it was being what Barry Levinson calls ''the motor that is going to drive the movie. Raymond being unchangeable, Charlie had to be the character that went from point A to point B.''

''He is a spiritual or emotional autistic for most of the story who finally learns to care for someone other than himself,'' Mr. Cruise explains. In the course of this change, there's another change: ''At the beginning,
there's this anger that Charlie carries with him against this man [ his father ] who wanted a perfect son and for whom nothing was ever good enough. But [ the film ] ends in his finally taking responsibility for a lot
of the anger in that relationship.''

Though Mr. Cruise is less voluble than Mr. Hoffman on his approach to his craft, Valeria Golino, the Italian actress who plays Mr. Cruise's co-worker and lover in ''Rain Man,'' contrasts Mr. Hoffman's reliance on ''pure
instinct'' with Mr. Cruise's more ''methodical'' attack. However, Mr. Hoffman found the younger actor remarkably similar to himself.

''We're both very compulsive and monklike,'' he notes. ''When we're shooting, we both like to work out, keep to a strict diet, not go out at night. And he writes his dialogue over and over in his own handwriting
- as if they're your own words, until you feel you are the writer - which is how I memorized 'Death of a Salesman.'

''Also,'' Mr. Hoffman adds, ''for the first time I was working with someone who was going through what I did 20 years ago - that first flush of stardom following 'The Graduate.' So we were linked into each other
- which allowed us to be rough with each other. There's an emotionality between us that's very difficult to act - that permitted moments to happen between us.''

Many of those moments unexpectedly involve humor - which comes from the conflict between Raymond's obstinate dedication to ritual and Charlie's intolerance of them. Are the film makers worried about violating good taste by inviting audiences
to laugh at the peculiarities of a disabled person?

While Mr. Hoffman snaps, ''I hate good taste - it's the most inhibiting thing in the world,'' he is also quick to point out that ''the thing was to remember the dignity of the character. You don't cheapen the character
if you don't violate him.''

For Barry Levinson, who last year found unexpected humor in war-torn Saigon in ''Good Morning, Vietnam,'' not violating the character consists mainly of letting each scene with Raymond find its natural balance between humor and seriousness.
''There are times in the movie where you laugh - and then you realize how sad it is,'' he says. ''And sometimes you see something and you say, Oh how sad that is - and all of a sudden you start
to laugh. The movie is constantly shifting, [ but ] we're not intentionally shifting it. . . You can't push - let's put a couple of laughs in here. You can't just suddenly go digging to get it; it just is.''

Mr. Levinson feels that it was probably the attempts of the directors previously associated with ''Rain Man'' to push and dig for action-adventure effects essentially foreign to the film's story that defeated them.

Reading the various drafts of the script indicated to Mr. Levinson that ''they kept. . . trying to bring something else into it, something that these characters worked against. That's the way they function - and that's valid. Most
movies are that way, I say, look, if we can create the characters strong enough, they're going to clash with one another - and that is the movie.

''I'm saying, the hell with the trains, the helicopters, the Mafia, the F.B.I., the car crashes, the pursuits, the stakeouts, the barricades.'' (Interestingly, ''Midnight Run,'' the
movie Martin Brest made instead of ''Rain Man,'' was about an odd couple played by Robert De Niro and Charles Grodin, who ''worked against'' most of these elements as they traveled cross-country.)
''The hell,'' Mr. Levinson reiterates, ''with all of those things that we pump into movies because we're afraid to make movies about people.''

Dustin Hoffman with Tom Cruise in a scene from "Rain Man." (United Artists)